The Brilliant Bit� Made from a solid brass body and stainless steel set screw, this bit will not corrode over time. Techniglass uses a proprietary diamond bonding technique to layer diamonds to the metal for a more uniform result. The design improves bit performance by reducing the amount of vibrations transmitted through the glass which produce fatigue cracks. Bit measures 3/4". Use standard coarse bits for the majority of your grinding jobs - it's a perfect medium between having quick grinding and a smooth finish.